The use of carboxylic acids and their salts is known in the art. U.S. Pat. No. 3,058,924 describes the use of formic acid as a blowing agent in polyurethane foams based upon adducts of hexahalocyclopentadiene and unsaturated monocarboxylic compounds. U.S. Pat. No. 4,417,002 describes a carboxylic acid or carboxylate reacted with an isocyanate to produce gas which is used as an effective blowing agent for polyurethanes. This invention describes such use in the manufacture of various types of urethane foams. The salts of formic acid found to be useful were those of formic acid with weak organic bases such as hydrazine, triethylamine, dimethylbenzylamine, and triethylenediamine. It is also disclosed that carboxylic acids and their salts are less exothermic than water in their reaction with isocyanates. U.S. Pat. No. 5,025,039 is directed to a process for the production of molded polyurethane foams having a compact surface and a density of at least 250 kg/m.sup.3 (15.6 pcf).
It has been found in the present invention that formic acid and its salts may be used not only as blowing agents but can also be used to tailor the reactivity profile of a given polyurethane foam system.